Top Considerations for Die Casting Design

Update:Dec 20 2016
Summary:

The die casting process is used in a variety of industr […]

The die casting process is used in a variety of industries to produce high-quality metal parts with close tolerances and fine surface finishes. When designing a part to be manufactured using a die casting process, several considerations must be taken into account so that the part can be successfully fabricated.

Some of the basic manufacturing and design considerations include draft, fillet, undercut, mold components, and post machining. The following are the detailed descriptions of these considerations.

Draft: The mold used to create a die-cast part has to be designed so that the part can be easily removed from the mold after the part has been cast and has cooled. Draft is a slight angle designed into the vertical surfaces of the die to allow easier ejection of the part from the die after the die casting process. Draft angles between 1º and 3º are common.

Fillet: A fillet is a radius at a corner where two surfaces meet, rather than having a sharp corner. An internal fillet reduces the stresses that occur in that location when the part is bent or stressed. And an external fillet radius is used to eliminate sharp edges.

Undercut: An undercut is a feature of the die cast part that prevents the piece from being ejected from the die after casting. Designs that require an undercut necessitate complex dies with removable slides so that the part can be extracted after casting. It is generally more cost effective to redesign the part to eliminate undercuts.

Mold Components: In order to create different design elements within a die cast part, several components are used within the mold. The die may also include removable slides or other sections to produce a component with recesses, undercuts, or cores. The use of these components increases the complexity of the mold design and the casting process, but their use generally results in less metal alloy being used and better tolerances throughout the part. Some of the mold components include:

Core: A core is a circular or other shaped section or pin that is used to create a void in a die cast part. The core can be movable or fixed, depending on the design of the part to be made.

Slide: A slide is a mold part that can be used to create voids or undercuts in the fabricated parts. Slides are usually incorporated parallel to the die parting axis. These components can be complex, allowing for design elements such as threads to be designed into a part.

Insert: A complex part can be generated using a pre-fabricated insert part that fits into the mold prior to casting. The insert is then encased in the die cast part and becomes part of the finished part. Other mold design considerations include the placement of gates for the flow of the molten metal and the inclusion of water lines for cooling the part after casting. Although these design elements do not contribute to the final design of the part, they are necessary parts of the mold design process.

Post-Machining: Depending on the design, it can be easier to perform post-machining on a die cast component rather than attempting to design the element into the part. For example, it may be easier to drill and tap a hole in a part rather than to design the threaded hole into the mold design. This simplifies the die casting mold and process, which saves time and money in manufacturing. The die casting process necessitates unique considerations to be taken during the design process. These considerations can be met through the use of specific design elements in the part and custom mold components.